referring to sound waves with frequencies higher than those at the upper limit of human hearing. Signals that are just above the frequency range of human hearing of approximately 20 kHz. [IAQG-history]

multidimensional attribute that relates to the impact a product has on its end-users. In general it refers to the efficiency with which a customer can do their tasks with the product, and their overall satisfaction with that product. [IAQG-history]